1. Field of the Invention
The present invention relates to a roller bearing having two rows of infinitely circulating roller rows, and to a roller type linear guide apparatus including a slider which moves linearly on a guide rail through the roller bearing.
2. Description of the Prior Art
A prior art roller type linear guide apparatus provided with a roller bearing of this type is known, for example, from U.S. Pat. No. 4,558,910. This linear guide apparatus, as shown in FIG. 13, includes a track base (guide rail) 11 extending in a longitudinal direction, a movable table (slider) 12 which is a long block body having a substantially inverted U-shaped cross section and disposed straddling the track base 11, and V type roller bearings 1 interposed between the track base 11 and the movable table 12. The tack base 11 is formed with ridges on both lateral sides so that the ridges extend horizontally and outwardly. Each of the ridges has at an extreme end, loaded roller rolling surfaces 13 constituted by upper and lower slant surfaces. On the other hand, the movable table 12 has a pair of V-shaped grooves 14 formed in inner surfaces of both side walls extending in the longitudinal direction, and has a bolt through hole 15 penetrating each of the side walls from a bottom of the V-shaped groove 14 to an outside surface of the side wall.
The V-shaped roller bearing 1 includes a bearing body 6 which is a long block body having a substantially square cross section, and it is provided with protruding ridges 2 and 3 respectively protruding from the centers of inner inclined surfaces 1a and 1a. The protruding ridges 2 and 3 have a track-like planar shape, and loaded roller surfaces 4 and 4 are formed on one side surfaces, and non-loaded roller surfaces 5 and 5 are formed on the other side surfaces. Cylinder rollers 7 circulate along a pair of loaded roller surface 4 and non-loaded roller surface 5. Roller retainers 8 and 8 are provided in parallel with respective inner inclined surfaces 1a and 1a of the bearing body 6 so as to guide the rollers 7 circulatably with a minute gap between an end face of the cylinder roller 7 and the roller retainer 8. The bearing body 6 is formed with a fixing screw hole 9 which penetrates from an edge at which outer inclined surfaces 1c and 1d intersect toward the inside of the bearing body 6 along a diagonal line.
The V-type roller bearings 1 and 1 are respectively fitted into the V-shaped grooves 14 and 14 of the movable table 12 so that the outer inclined surfaces 1c and 1d of each V-type roller bearing 1 are in contact with the inner surfaces of the V-shaped groove 14. A bolt 16 which passes through the bolt through hole 15 engages the fixing screw hole 9 to secure the V-type roller bearing 1 to the movable table 12. Thus the loaded rollers B1 are in contact with the loaded roller rolling surfaces 13 of the track base 11 and roll as the movable table 12 is moved.
In the prior art roller type linear guide apparatus, the loaded rollers B1 of the V-type roller bearing 1 are disposed on the inner surfaces inclined in a V shape. These upper and lower loaded rollers B1 and B1 which are disposed close to each other sandwich the V-shaped loaded roller rolling surfaces 13 and 13 formed on the extreme end of the ridge protruding horizontally from the track base 11. However, the V-type roller bearing 1 is merely secured to the movable table 12 with the bolt 16 which extends in only one direction horizontally. As a result, a problem is involved in that the rigidity is low with respect to a moment load M in a rolling direction of the movable table 12.
Furthermore, in the prior art roller bearing 1, the cylindrical roller 7 is merely held circulatably by the roller retainer 8 fixed to the bearing body 6 with the minute gap between the end face of the cylindrical roller 7 and the roller retainer 8. As a result, when the V-type roller bearing 1 is removed from the track base 11, the loaded rollers B1 will fall off the V-type roller bearing 1.
Accordingly, in order to prevent the fall off of the rollers, and to facilitate the assembling of the V-type roller bearing 1, it has been proposed as shown in FIG. 14, to fix a fall-off preventing roller retainer 17 to an inner recessed portion of the bearing body 6. The roller retainer 17 has a substantially U-shaped cross section and extends in the longitudinal direction thereby to hold a part of an inner peripheral surface of the loaded roller B1 rollably. However, in this case, since the roller retainer 17 is a long member having a complicated cross sectional shape, a problem arises in that the manufacture is troublesome, the cost of a metal mold is expensive, and the rolling of the loaded roller B1 is apt to be hindered due to a manufacture error and an assemble error.
Furthermore, in the prior art V-type roller bearing 1, since the screw hole 9 for the fixing bolt is formed in the bearing body 6 diagonally from the edge at which the outer inclined surfaces 1c and 1d intersect towards the inside of the bearing body 6, there is a problem in that the hole forming work and the tapping work for the bolt screw hole 9 are very difficult.
Moreover, since the V-type roller bearing 1 is fixed by the bolt 16 from only one direction, another problem is present in that when an intersection angle between the inclined surfaces 1c and 1d is small, looseness or shake is apt to be produced easily when a fixing angle is deviated even slightly. Specifically, the intersection angle between the inclined surfaces 1c and 1d of the roller bearing 1 is not always exactly the same as the intersection angle between the corresponding inner inclined surfaces of the V-shaped roller mounting groove of the slider due to manufacture error of the product. When the intersection angle between the inclined surfaces 1c and 1d of the roller bearing 1 is smaller than that of the V-shaped roller mounting groove, a gap will be caused between one of the inclined surfaces 1c and 1d and its corresponding inner inclined surface of the roller mounting groove, or gaps will be caused at both sides of the inclined surfaces of the roller bearing 1. In this case, since the roller bearing 1 is secured to the V-shaped roller mounting groove with the single bolt 16 which passes through the apex of the inclined surfaces 1c and 1d of the roller bearing 1, the roller bearing 1 is apt to be shaked due to the presence of the gap or gaps. Thus, even when the bolt 16 is clamped securely, the rigidity of the roller bearing with respect to the V-shaped roller mounting groove is small.